Production of radio tubes for the German Army started in 1937, and was followed by the building of communication sets and similar electronics.

World War II began with Germany invading Poland on 1 September 1939. Lorenz was already a major supplier for the German Military, and soon greatly expanded its production facilities.

Military products from Lorenz during World War II included land-based and airborne radar, two-way radio sets, wire recorders, radio tubes, and Germany's most secure communications device, the Lorenz Cipher machine.

At the high point of the war, Lorenz had about 24,000 workers in 12 operating facilities.